The present invention relates to a heat exchanger to be used for a refrigerating cycle mounted on a vehicle or the like, a method of manufacturing the heat exchanger and a method of manufacturing a tube for heat exchange.
Conventionally, the heat exchangers to be used for the refrigerating cycle of vehicles and others are comprised of stacking a plurality of flat tubes, mounting fins between the stacked tubes, and connecting either end of the tubes to tanks. A heat exchange medium flowing from another apparatus of the refrigerating cycle into the tanks is distributed to the respective tubes to make heat exchange with outside air through the tubes and fins.
Generally, the tubes used for the heat exchangers are formed into a flat cross-sectional shape by joining the ends of one or two plates. Forming to have the flat cross-sectional shape is to enlarge a contact area between the fin and the tube so to efficiently conduct heat of the medium from the heat exchange tubes to the fins, thereby improving heat exchange performance.
For example, as shown in FIG. 11, a flat tube 2 is formed by bending a single plate at about its center to form a U-shaped cross section so to form beads or the like, and brazing to mutually adhere the opposed surfaces of both ends 2h, 2h of the plate.
The tubes 2 formed to have the flat cross-sectional shape are fitted with fins and alternately stacked to form a core, the both ends of the tubes 2 are fitted to tanks and brazed to form a heat exchanger 1.
But, the tube 2 having the opposed surfaces of the both ends 2h, 2h of the plate contacted with each other had a possibility that the portions, where the both ends 2h, 2h are joined, would open before or at brazing to degrade the assembling property of the tubes 2 and the tanks or to cause defective brazing.
And, when the tube 2 was formed by joining the both ends 2h, 2h of the plate, the joint portion had a shape protruded from the other portion of the tube, so that there was a possibility of causing defective brazing because tube insertion holes of the tanks into which the tubes were inserted became complex and a gap was formed between the tube fitted to the tube insertion hole and the tube insertion hole.
In addition, a heat exchange tube 40 described in Japanese Patent Application Laid-Open Publication No. Hei 10-274489 has fold-back portions 41, 41 which are formed by bending to fold back the ends of two plates which configure a tube, and which are mutually joined on the fold-back outer surfaces as shown in FIG. 12.
The heat exchange tube 50 described in Japanese Patent Application Laid-Open Publication No. Hei 11-248383 forms fold-back portions 51a, 51b at the ends of two plates, caulking the fold-back portions 51a, 51b after joining them mutually, and brazing the caulked portion as shown in FIG. 13.
But, the aforesaid tube 40 is formed to have a gap 42a in a triangle cross-sectional shape at the joint portion 42 where the fold-back portions 41, 41 are joined.
The tube 50 is also formed a gap 52a having a triangle cross-sectional shape in a joint portion 52 where the fold-back portions 51a, 51a are joined.
These gaps 42a, 52a having a triangle cross-sectional shape are not supplied with a sufficient amount of flux or a brazing material, resulting in the possibility of causing defective brazing.
When usual sizing is performed, the ends of the plates are rolled in a direction of the insides of the tubes 40, 50, and there is a disadvantage that the gaps 42a, 52a having a triangle cross-sectional shape are not filled with extra thickness of the plates.
And, a heat exchanger using the aforesaid tubes, such as a condenser, is generally mounted at the front or a lower part of a vehicle.
Therefore, a small stone or the like having entered from the outside into the vehicle tends to hit the front of the condenser and becomes a cause of breaking the tubes to leak a medium or the like, resulting in a problem that the air conditioner does not work.
Accordingly, it is an object of the present invention to improve an assembling property and a brazing property by preventing the joint portion of the tube from opening and modifying the peripheral shape of the tube, and to provide a heat exchanger using tubes resistant to stone hitting or the like, a method of manufacturing the heat exchanger and a method of manufacturing the tubes for the heat exchange.
The invention described in claim 1 is a heat exchanger comprising a core which is consisting of tubes provided with medium passages and fins fitted to the tubes, and tanks to which ends of the tubes are connected, wherein the tube is formed to have a flat cross-sectional shape by joining ends of one or two plates, the tube has a contact portion which is formed by bending at least one of the plate ends a plurality of times and overlaying the plate end on the other plate end, and a joint portion which is formed by placing a part of the contact portion on the top or bottom flat surface of the tube and mutually engaging the both ends of the plate.
For example, when a pressure is applied in directions of the top and bottom flat surfaces of the tube, an extra thickness at the end of each plate configuring the tube escapes in the direction of the mutually engaged contact portions, and the gaps in the contact portions are filled.
Therefore, the peripheries of the tube are restricted to within the tolerance of a predetermined dimension.
Thus, the tubes are improved in the assembling property with the tanks, and the gaps in the contact portions of the tubes are eliminated, so that adhesion between the tube insertion holes of the tanks and the peripheries of the tubes is improved, and the brazing property can be improved.
The invention described in claim 2 is the invention according to claim 1, wherein the tube is provided with a joint portion which is formed by fully covering the end of the tube with one of the plate ends and mutually engaging the both plate ends.
Here, the end of the tube means at least one of the ends of the tube.
For example, when sizing is performed to apply a pressure in the top and bottom flat surface directions of the tube, the extra thickness of the plate end produced by the application of pressure escape in a direction intersecting at right angles with the direction that the pressure is applied, so that the gap between the mutually engaged contact portions is filled with the extra thickness.
Therefore, the tube is restricted its periphery to within the tolerance of a predetermined size.
Thus, because the tube""s assembling property with the tanks is improved and no gap is caused between the contact portions of the tubes, adhesion between the tube insertion holes of the tanks and the tube periphery is improved, and the tube can be improved its brazing property.
The invention described in claim 3 is a heat exchanger comprising a core which is consisting of tubes provided with medium passages and fins fitted to the tubes, and tanks to which ends of the tubes are connected, wherein the tube is provided with a joint portion which is formed by contacting at least one plate end surface to the other plate end, and the joint portion is such that one plate end surface is engaged with the other plate end brazed to prevent the tubes from opening.
When the tubes are prevented from opening, the assembling property of the tubes and the tanks becomes good. And, because the tubes are prevented from opening, the brazing property between the tubes and the tanks is improved, and it becomes possible to provide a quality heat exchanger free from a leakage of the medium or the like.
The invention described in claim 4 is the heat exchanger according to any of claims 1 to 3, wherein the joint portion of the tube uses a tube in which a portion positioned on at least the periphery of the tube is present in the same peripheral surface as the outer peripheral surface of the tube configuring the medium passages.
Thus, the joint portion of the tube has the portion positioned on at least the periphery of the tube present in the same peripheral surface as the outer peripheral surface of the tube configuring the medium passages, and the joint portion is not protruded.
Therefore, the tube insertion holes to be formed on the tanks can be made to have a simple shape, and the tube insertion holes can be formed with ease.
And, since the tube periphery and the tube insertion holes have a simple shape, no extra gap or the like is formed between the inserted tube and the tube insertion hole, and adhesion can be enhanced to improve the brazing property.
The invention described in claim 5 is the heat exchanger according to any of claims 1 to 4, wherein a vertical height of the joint portion is the same as that of the other portion excepting the joint portion of the tube having the medium passages.
Thus, when the height of the joint portion of the tube has the same size as the vertical height of the other portion excepting the joint portion of the tube, the joint portion does not protrude from the tube periphery, and the peripheral shape of the tube has a simple shape.
Therefore, the tube insertion hole in which the tube is inserted can be made to have a simple shape, and no extra gap is formed between the tube and the tube insertion hole, enabling to improve the assembling property and the brazing property of the tube and the tank.
The invention described in claim 6 is the heat exchanger according to any of claims 1 to 5, wherein the joint portion of the tube has at least one plate end surface within the joint portion.
Thus, the tube has at least the one plate end surface in the joint portion, so that the plate end surface can be engaged with the other plate end portion to prevent the tube from opening.
Therefore, the assembling property of the tube and the tank is improved, the brazing property between the tube and the tank is improved, and it becomes possible to provide a quality heat exchanger free from a leakage of the medium or the like.
The invention described in claim 7 is the heat exchanger according to any of claims 1 to 6, wherein the tube is provided with projections toward the medium passages.
Thus, when the projections are disposed in the medium passages of the tube, turbulence can be caused in the medium flowing through the medium passages, to improve the heat exchange efficiency.
The invention described in claim 8 is the heat exchanger according to any of claims 1 to 7, wherein the tube has the core which is comprised of the tubes and the fins brazed with the tanks.
Thus, the fins are mounted between the tubes or on the sides of the tubes to form the core in their multiple layer, the tubes are connected to the tube insertion holes of the tanks, and the tubes, fins and tanks are assembled.
And, the tubes, fins and tanks are integrally brazed in a furnace to form the heat exchanger.
The invention described in claim 9 is the heat exchanger according to any of claims 1 to 8, wherein the joint portion is disposed on one side surface of the core.
Thus, the heat exchanger of this example is formed with the joint portions of the tubes gathered to one side face of the core.
And, to mount on a vehicle body, the heat exchanger is mounted with the side face having the gathered joint portions directed toward the front of the vehicle body.
As described above, the joint portions are thicker than the other portion because at least one plate end is engaged with the other plate end portion and overlaid.
Therefore, by disposing the thick joint portion at the front of the vehicle body, an impact strength of the heat exchanger is improved, and a breakage due to stone hitting or the like can be prevented.
The invention described in claim 10 is the heat exchanger according to any of claims 1 to 9, wherein a cross-sectional profile of the joint portion has an arc with a diameter greater than the tube height on at least a part thereof.
The cross-sectional profile of the joint portion has an arc with a diameter larger than the vertical height of the tube, and the arc portion is made closer to a straight line.
Thus, when the profile of the joint portion of the tube is made to be closer to a straight line, a joint length of the fin and the tube is increased, so that the thermal conductivity is improved, and the heat radiation performance of the heat exchanger is improved.
The invention described in claim 11 is the heat exchanger according to any of claims 1 to 10, wherein the joint portion has a linear portion on a cross-sectional profile of the joint portion.
Thus, because the joint portion of the tube has the linear portion on the cross-sectional profile of the joint portion, a joint length of the fin and the tube is increased, the thermal conductivity is improved, and the heat radiation performance of the heat exchanger is improved.
The invention described in claim 12 is the heat exchanger according to any of claims 1 to 11, wherein the tube is formed to have a symmetrical shape in its breadthwise cross-sectional shape.
Thus, when the cross-sectional profile of the tube in its breadth direction is symmetrical, the tube insertion holes of the tank can be made to have a simple shape, formability of the tube insertion holes and the assembling property of the tubes and the tanks can be improved.
And, improper assembly that reversing the breadth direction of the tube symmetrically can be prevented.
The invention described in claim 13 is a method of manufacturing a heat exchanger comprising tubes having medium passages and performing heat exchange of a medium flowing through the medium passages, a core having the tubes and fins alternately stacked, and tanks to which the tube ends are mounted, the method comprising the steps of forming the tubes by bending a plate, sizing the formed tubes, and brazing the sized tubes.
Thus, the method of manufacturing the heat exchanger of the present invention has the step of sizing the formed tubes. After forming the tubes, deviations caused in the joint portions of the tubes are filled with the extra thickness produced by the pressure applied when sizing, and the periphery of the tube is limited to within the tolerance of a predetermined dimension.
Therefore, the assembling property and the brazing property of the tubes with other members are improved, and the quality heat exchanger can be provided.
The invention described in claim 14 is a method of manufacturing tubes for a heat exchanger comprising the steps of forming a bent portion which configures portion by bending at least one end of a plate, bending the plate into a flat shape, and engaging the formed end having the bent portion with the other end.
The plate has at least one end being bent to form the bent portion and bent at about the center of the plate into a U shape or another shape to form a tube having a flat cross-sectional shape, then the bent portions previously formed are mutually engaged to form the joint portion so to form the tube having a flat cross-sectional shape. Subsequently, the formed tubes are entirely sized to limit the tube peripheries to within the tolerance of a given dimension.
Thus, by limiting the tube peripheries to within the tolerance of the given dimension, the assembling property and brazing property of the tube insertion holes formed on the tanks and the tubes are improved, and a quality heat exchanger free from a leakage of the medium or the like can be provided.